Pension and Other Postretirement Benefit Plans (Schedule of Weighted-Average Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate (as a percent)	3.65%	4.31%
Rate of compensation increase (as a percent)	3.73%	3.90%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (as a percent)	4.27%	4.52%	4.07%
Expected long-term return on plan assets (as a percent)	6.90%	7.25%	7.75%
Expected long-term return on plan assets (as a percent)	3.90%	3.80%	3.80%
Other Postretirement Benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate (as a percent)	3.65%	4.22%
Rate of compensation increase (as a percent)	0.00%	0.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (as a percent)	4.22%	4.50%	4.03%
Expected long-term return on plan assets (as a percent)	0.00%	0.00%	0.00%
Expected long-term return on plan assets (as a percent)	0.00%	0.00%	0.00%